Forest trees remember their roots

U. TORONTO (CAN) — When it comes to how they respond to the environment, trees may not be that different from humans.

Recent studies show that even genetically identical human twins can have a different chance of getting a disease, because each twin has distinct personal experiences through their lifetime.

It turns out that the same is likely true for forest trees.


“The findings were really quite stunning,” says Malcolm Campbell, a biologist at the University of Toronto and lead author of the study. “People have been talking about a so-called nursery effect for a long time.”

The study, published in the journal Proceedings of the National Academy of Sciences, examined the theory that trees and other plants, even when they are genetically identical, grow differently and respond differently to stress, depending on the nursery that the plants are obtained from.

“Our results show that there is a form of molecular memory in trees where a tree’s previous personal experience influences how it responds to the environment.”

For the new study, graduate student Sherosha Raj used genetically identical poplar trees that had been grown in two different regions of Canada. The stem cuttings were then used to regrow the trees under identical climate-controlled conditions in Toronto. Half of the trees were subjected to drought conditions while the remaining trees were well watered.

Since the trees were regrown under identical conditions, Campbell predicted all the specimens would respond to drought in the same manner, regardless of where they had come from.

Remarkably, genetically identical specimens of two poplar varieties responded differently to the drought treatment depending on their place of origin.

This difference occurred at the most fundamental level—the one of gene activity. Even though the specimens were all genetically identical, trees that had been obtained from Alberta used a different set of genes to respond to drought than the ones that had been obtained from Saskatchewan.

The findings are relevant to foresters and gardeners in highlighting the importance of the nursery source for trees and other plants, which can determine how the plant will grow and resist stress in a forest or the garden.

Additionally, the memory of previous experience could also help determine plant survival in response to changes in climate, or other environmental stresses like diseases or pests.

Researchers from the University of British Columbia, Simon Fraser University, and the University of Alberta contributed to the study, that was supported by Natural Sciences and Engineering Research Council of Canada, Alberta Pacific Forest Industries, and Agriculture and Agrifood Canada.

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